Metallurgy.



H. s. KIMBALL.

METALLUR'GY.

APPLICATIQN FILED FEB. 4. i914.

1,189,830. Patented Ju1y4,1916.

mann errar @MNHN @HQE HENRY SWIFT KIMBALL, OJE STILOUIS, MISSOURI, ASSIGNOR TO AMERICAN ZINC LEAD & SIVIELTING COMPANY, F BOSTON, MASSACHUSETT, A CORPORATION 0F MAIN'E.

, METALLURGY.

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Specification of Letters Patent.

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Application led February 4,1914. Serial No. 816,399.

from a gaseous to a liquid condition, andy has for its object the `promotion of condensation, or transition from the gaseous to the liquid condition of such metallic substances; z'. e. metals of which the reduction temperature is higher than the boiling point of the metal.

As my invention is applicable to the met allurgy of zinc, it will be herein described in that connection. l

The present usual method of smelting zinc ore for-the metal, a method empirically determined and fixed by the practice' of more than a century, involves the costly procedure 'of reduction of Zinc oXid (obtained at presentvfor the most part by roasting the natural sulid ores) with carbonaceous material, in small isolated charges ofV about 100 pounds within clay retorts heated externally in a gas furnace, to about 1400 degrees 'centigrade. Jlutter the preliminary expulslon of water vapor and coal gas from the retort, the zinc is reduced by the carbon, and to` gether with carbon monoXid, vdrifts from the retort into the condenser, which is a conical clay extension luted into the end of the re tort. The difficulties of condensation oit' the Zinc gas to metallic Zinc, have been largely responsible for the present state of the art. Under the best conditions of condensation in the condenser, the yield of metallic zinc is high, running to 90% and over in commercial operation. But at certain stages 1n the reduction of a retort charge, or under orc conditions, temperature conditions, etc., which fall short of the empirically ascertained standard of practical erfection, the losses due to formation of blue powder and waste of Zinc by escape and combustion,

frequently reach a ruinously high percent- The chief cause of loss is the forma,-A

age. tion of blue powder, which to the best of present knowledge consists oi extremely minute particles of zinc on the surface of which zinc oxid has Jformed, this oXid preventing the agglomeration of the small par ticles into largerdrops of metallic zinc in the condenser. As it is very difiicult to fuse this blue powder at. practicable tempera tures it is common practice to replace it in a retort together with a little reduction mate rial and again reduce the zinc.

By the invention herein described, larger percentages of coherent metallic zinc are precipitated from retort gas than would otherwisel be the case, and also metallic Zinc can be condensed and' recovered under conditions in which, by means of processes heretoore practised, only blue powder would resu t.

Generally speaking, this invention is characterized by electrical 'excitation of the region" where a substance in gaseous condition or in gaseous solution, as for instance zinc, exists and is at or near the temperature of condensation, and the provocation or promotion of condensation of the substance to the liquid form by such electrical excitation. This effect is producible by the maintenance of an electrical field either with or without convective discharge, and to a greater or less extent may be produced by either unidirec- Y tional or alternating, stress in an electrical eld. The net practical result of subjecting a zinc gas or vapor region to the influence of electrical field is: that the condensation of metallic zinc under the best smelting conditions, is slightly improved; the condensation of metallic Zinc under inferior smelting conditions is very emphatically improved; and

the electrical field, imposed upon'conditions' which otherwise` would preclude the production of anythina eXceptblue powder, causes condensation oth metallic zine. An explanation of this practical result cannot be oered with anyn great degree of confidence,l since we are doubtless dealing with inter-atomic relations. Probably one aspect of the action of the electrical field is analogousto the agglomerating action on water' vapor of the lelectric discharge during electric storms.

Another aspect of it is probably the produc tion of an` abnormal or artificial dew point,

lwhich would provoke condensation from an atmosphere only saturated with referenceto the normaldew poi-nt; Obviously, either or both'of'the above actions would take place whether the electrical stress be direct or alternating. lt seems reasonable to suppose that the agglomerating action of the electric field is due to a speeding up of the zinc molecules or particles, so that they collide with each other more frequently than they otherwise would. Probably also, another eHect,

particularly in the case of direct current (or current in which one phasel predominates) whether or not qualified by spray discharge, is toV drive the particles of zinc mist together, locally increasing the density of the zinc mist after passing from the gaseous to the cloud stage, giving the particles increased opportunity for bombarding each other and the walls of the containing vessel. There may be still another effect; that the zinc particles are electrically charged and more or less Ydissociated at the high temperaate diminution of deposited blue powder.

In the drawing hereto annexed there is shown, in diagram, an apparatus suited t0 the performance of my process. This apparatus is not claimed herein, but forms the subject matter for another application for patent.

Referring to the drawing: 1 represents the end of a Zinc smelting retort.

2 represents the condenser, luted into the end of the retort 1.

3 represents an upward extension of the condenser.

4 represents a spout from which metallic zinc (Z) may be tapped.

5 is a curtain formed at the head of spout 4.

6 is a dam in the spout 4, forming with the curtain 5 a trap, to be sealed by metallic zinc.

7 is a screen, built at the retort end of the condenser, to close all but the top of the inner end of the condenser.

8 is a cylindrical cowl, placed over the top of the conical extension 3, and preferably luted thereto.

9 is a tube through which the gases escape into the atmosphere, secured through the top of the cowl 8.

10 is a spider, to support the tube 11 centrally in the tube 9.

11 is a tube of refractory insulating material, preferably fused quartz, suspended centrally in the larger tube 9.

12 is a conductor, leading from the source of electric potential at S. The conductor 12 passes through tube 11, and out therefrom into the condenser cone 3, where, if desired, the condenser may be armed with sharp. prointo the condenser cone should be made of.

metal which will persist unaltered under the conditions of operation. The alloy nichrome has been found quite suitable.

G represents the ground connection from the electrical source S.

S represents a source of electrical potential, which may be director alternating in character. i

Z represents the pool of metallic zinc in the lower part of the condenser, trapping the same at 5, 6.

14 represents a region where, under electrical influence the zinc condenses in liquid form, to flow down the sides of the condenser toward the pool at Z. K

15 shows the direction of eflluX of carbon monoxid, which burns on escape into the air.

16 is a hand hole cover which may be removed to clean out the condenser.

The operation of the apparatus is as follows: Carbon monoXid and gaseous zinc, delivered from the charge in the retort 1, flow gently over the screen 7 and often through a mass of incandescent carbon in the mouth of the condenser back of the screen 7 into the condenser 2, 3, cooling as they flow toward the outlet through tube 9. Direct current-say-is supplied from the source S, the voltage delivered being fairly high, say- 5000 to 6000 volts. The electric quantity, of course, is proportionately small. If the conditions before applying the electric current were such that zinc flame appeared at 15, it will he observed that the application of electric current is followed immediately by cessation of zinc llame. The condenser 2, 3 being grounded to all practical intents, the circuit is completed to ground. Zinc in liquid form, condensesv at the zone 14, and runs in drops ldown the sides of the condenser 2, 3. The proportion of blue'powder s reduced' below what would result in the absence of the electric field, and metallic zinc is yielded, though the retort conditions are such that such zinc yield would be precluded were the electrical field not maintained.

An important, if not the chief, reason why it has proved impracticable heretofore to smelt zinc in furnaces of large capacity and by continuous processes, such as are suited to the reduction of other metals, is, that the conditions of reduction of zinc compel the use of temperatures at which zinc when reduced is a gas, and the metal, at the critical temperature of condensation, is hypersensitive to oxidation, and still at low density, is easily carried away by currents.

What .I claim and desire to secure by Letters Patent is:

1. The method of promoting and insuring liquefaction by condensation of a metal from a gas thereof, which consists in subjecting nieces() the metallic gas when at or near the ternperature of condensation, to a field of electric stress, thereby accelerating the agglomeration of liquefying particles and preventing individual oxidation thereof.

2. The method of promoting and insuring liquei'action by condensation of Zinc from the gas thereof, which consists in subjecting the zinc gas when at or near the temperature of condensation to a iield of electric stress, thereby accelerating the agglomeration oi' liqueiying particles and preventing the formation of blue powder.

3. The method of promoting and insuring liquefaction by condensation of eine from the gas thereof, which consists in subjecting the zinc gas when at or near the temperature of condensation to a field of electric stress, characterized by convective discharge, thereby accelerating the agglomeratien of liquefying particles and preventing the formation or blue powder.,

Signed by me at St. Louis, Missouri, this twenty-first day of January, 1914..

HENRY SWIFT KIMBALL. TWitnesses:

ALBERT E. JENKINS, A. l. MCDANIEL. 

